US3336453A

US3336453A - Means for controlling the blast valve and contacts of a gas blast circuit breaker

Info

Publication number: US3336453A
Application number: US421776A
Authority: US
Inventors: John W Beatty; Richard H Miller
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1964-12-29
Filing date: 1964-12-29
Publication date: 1967-08-15
Anticipated expiration: 1984-08-15
Also published as: FR1462615A; GB1098380A; DE1515789A1; US3336454A; CH457583A; DE1515781A1

Description

Aug. 15, 157 j w. BEATTY ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29. 1964 5 $heetsSheet l F/GJ.

ATMUJPHEfi/O PRESSURE 70Gb PRESSURE uvvavrom: JOHN W. 55%17'7'), R/cH/uw H. M/LLER A TTOR/VEY Aug. 15. 197 J.W. BEATTY ET AL MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER Flled Dec. 29. 1964 5 Sheets-Sheet 2 H/G/v PRESSURE INVENTORS. 7 JOHN W. BEATTY R/cHA/w H. M/LLER ATTORNEY Aug. 15, 1967 J E Y ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER 5 Sheets-Sheet 5 Filed Dec. 29. 1964 IN VENTORS.

ATTORNEY mg. 15, W67 J.W. BEATTY ET AL 3 9 MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29, 1964 5 Sheets-Sheet 4 ATTORNEY Aug. 15, H967 ,w BEATTY ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29, 1964 5 Sheets-Sheet 5 /7Za m4 /72 L70 m1- /7 O O O INVENTORS.

JOHN W. 55/477), R/CHARD M/LLER 5y 0mm 7L A ATTORNEY United States Patent 3,336,453 MEANS FOR CONTROLLING BLAST VALVE AND CUNTACTS OF A GAS BLAST CHRQUH" BREAKER John W. Beatty, Newtown Square, and Richard H. Miller, Berwyn, Pa., assignors to General Electric Company, a corporation of New York Filed Dec. 29, 1964, Ser. No. 421,776 17 Claims. (til. 200-148) This invention relates to an electric circuit breaker of the gas blast type and, more particularly, relates to means for controlling the blast valve and movable contacts of such a circuit breaker.

In the circuit breaker of the present invention, there is a pair of relatively movable contacts that can be separated to draw an arc therebetween and a blast valve that is operable at the time of contact-separation to cause a blast of pressurized gas to flow through the arcing region to aid in extinguishing the arc. The blast valve comprises a movable valve member that can be operated from a normally-closed position to an open position to create the gas blast. After a period of time suflicient to insure extinction of the arc, the movable blast valve member is returned to its normally-closed position to terminate the blast, thereby preventing such wastage of pressurized gas as would result from continuation of the blast. The con tacts are held in open position after the blast valve closes, thus maintaining the circuit open.

An object of our invention is to provide a new and improved mechanism for controlling the blast valve and contacts in this manner.

In certain prior mechanisms for controlling the blast valve and contacts, the same pressurized fluid has been used for both returning the movable blast valve member to its closed position and for holding the contacts in open position. When it has been desired to close such a circuit breaker, the pressure of the pressurized fluid holding the contacts open had to be reduced to a predetermined level, as by venting, before closing motion of the contacts could begin. Thereafter, the speed of closing depended upon the rate of venting. In certain circuit breaker applications, it is disadvantageous to rely upon such venting because it requires a rather long time that unduly delays initiation of contact-closing motion. Another disadvantage of relying upon such venting is that closing times tend to vary rather widely with variations in the initial fluid pressure holding the contacts open.

Another object of our invention is to provide an operating mechanism capable of controlling the motion of the blast valve and contacts in the general manner set forth above but capable of responding faster to a closing signal and capable of more precisely controlling contact-closing motion than a mechanism that relies upon the above-described venting of pressurized fluid for initiating and controlling closing motion.

Another object is to provide a blast valve and contact operating mechanism which can initiate circuit breaker opening in response to a relatively low-force input signal and within a very short time after reception of the input signal.

Still another object is to provide a high speed blast valve and contact operating mechanism that is highly compact and can be located in a small gas-filled tank surrounding the contacts.

Another object is to provide an operating mechanism which has opening time characteristics that are relatively insensitive to minor changes in the position of an operation-initiating part.

In carrying out our invention in one form, we provide a gas blast circuit breaker that comprises a contact movable from a closed position to an open position to develop 3,335,453 Patented Aug. 15, 1967 an arc, a blast valve member movable from a closed position to an open position to create an arc-extinguishing blast, and a tank that is adapted to contain a supply of high pressure gas in which the contact is located. Coupled to the movable blast valve member is an actuating piston that has an opening surface on which pressurized fluid is adapted to act in a blast valve-opening direction and a closing surface on which pressurized fluid is adapted to act in a blast valve-closing direction. Means is provided for supplying high pressure fluid to the opening surface of the actuating piston to drive the piston through an opening-stroke that opens the blast valve member. Actuating means coupled to the contact is provided for transmitting contact-opening motion from the actuating piston to the contact when the actuating piston moves through its opening stroke. Means is also provided for supplying high pressure fluid to the closing surface of the piston after the opening stroke to then cause closing of the blast valve member. When the blast valve member is closed, the closing surface is vented to a low pressure region, and this removes from the closing surface high pressure fluid that previously acted on the contact in an opening direction. Closing means is provided for causing the high pressure gas in the tank when the closing surface of the blast valve piston is vented to the low pressure region to exert a net force on the contact acting in a direction to drive the contact toward closed position. Latching means is provided for holding the contact in an open position against this closing means when the closing surface of the piston is vented to the low pressure region, and closing control means is provided for releasing the latching means to permit the closing means to drive the contact into closed position.

For a better understanding of our invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic side elevational view partly in section of a circuit breaker embodying one form of our invention.

FIG. 2 is a cross sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is a schematic cross sectional view taken along the line 3-3 of FIG. 2; FIG. 3 shows the circuit breaker in its normally-closed position.

FIG. 4 is a schematic cross sectional view similar to FIG. 3 except showing the circuit breaker in a position in which its blast valve and contacts are fully open.

FIG. 5 is a schematic view partly in section also showing the circuit breaker in its normally-closed position.

FIG. 6 is a view similar to FIG. 5 except showing the circuit breaker in its fully-open position. FIG. 6 illustrates the position of the parts when the circuit breaker has just entered its fully-open position, and, accordingly, the normally-closed blast valve is still open but is in readiness to reclo-se.

General description of circuit breaker Referring now to FIG. 1, the circuit breaker shown therein comprises a metallic tank 10 filled with a highly pressurized gas, preferably air. This tank 10 is mounted on a tubular insulating column 12, preferably of porcelain, that isolates the tank from ground.

Projecting into the tank ill from opposite sides thereof are two insulating bushings 14 and 16. Each of these bushings comprises a centrally-disposed rigid conductor 18 and a tubular insulator 20 surrounding and supporting the conductor 18 and insulating it from the tank 10 when the circuit breaker is open.

At the inner end of each of these conductors 18 is a stationary contact 22;. Cooperating with their respective stationary contacts 22 are a pair of movable contacts 24, each of which is pivotally mounted at 26 on a central a casting 28 that is mounted on the tank It) and electrically connected thereto. When the circuit breaker is in its closed position, as shown in FIG. 1, an electrical circuit extends through the circuit breaker via one conductor 18, one pair of contacts 22, 24 through the central casting 28, the other pair of contacts 22, 24, and the other conductor 18.

During a circuit breaker opening operation, the contacts 24 are simultaneously operated from their closed position of FIG. 1, into their open position by driving a centrally disposed crosshead 30 in a downward direction. This crosshead 30 is coupled to the contacts 24 by means of links 32, each of which is pivotally, connected at its opposite ends to a contact 24 and the crosshead 3tB. Whcn the crosshead moves downwardly from its position of FIG. 1, it acts through links 32 to pivot the movable contacts 24 about their pivots 26, moving the upper portion of each movable contact 24 toward the central casting, thus separating the movable contacts 24 from their respective stationary contacts 22.

The above-described contact-separation produces an arc between the contacts of each pair, and this arc is extinguished after a short interval by a blast of pressurized gas which flows through the arcing region. This gas blast is produced by opening a normally-closed blast valve 35 just prior to the time the contacts separate to form the arc. The normally-closed blast valve 35 comprises a movable valve member 36 that is located in a blast passage 37. This blast passage 37 extends upwardly to atmosphere from two nozzles 38 respectively located adjacent the two arcing regions. When the movable blast valve member 36 is moved in a downward opening direction from its position of FIG. 1, pressurized gas flows from the tank 1!) through the nozzles 38 and blast passage 37 via paths such as illustrated by arrows 40. After the movable blast valve member has remained in open position for a sufficient period to effect arc-extinction, it is returned to its closed position of FIG. 1 to terminate the gas blast. This valve-closing prevents the pressurized gas in the tank from being wasted by continued flow fro-m the tank after a circuit-interrupting operation. The contacts are normally caused to remain open after an interrupting operation to maintain two series-related intercontact gaps in the circuit through the circuit breaker.

Operating mechanism for blast valve and contacts For controlling the movable blast member 36 and the movable contacts 24 in the above-described manner, a pneumatically-controlled operating mechanism 56 located in the hollow casting 28 is provided. This operating mechanism 50 is best shown in FIG. 3. It comprises a stationary centrally-located cylinder 52 that is normally filled with pressurized gas from the tank 10. This pressurized gas is supplied from the tank through a feed passage 56 having ports 57, 58, 59 and opening into the interior of the stationary cylinder 52. The stationary cylinder 52 has a lower end wall 53 and an upper end wall 54.

Slidably mounted within the stationary cylinder 52 is a contact-opening dashpot piston 69 that is rigidly connected to the crosshead 30. The dashpot piston 66 has a vertically-extending piston rod 61 that extends through the lower end wall 53 of cylinder 52 and is suitably joined to a portion 150 of the crosshead 30. In this latter respect, a threaded portion of the piston rod 61 extends through the portion 150 of crosshead 3i), and a nut 62 is threaded thereon to clamp the crosshead portion 156 between the nut 62 and a shoulder on the piston rod 61. Also secured to the crosshead 30 is a plurality of rods 64 that project upwardly from the crosshead about the outside of cylinder 52. As will soon appear more clearly, contact-opening forces are transmitted through these rods 64 to effect downward opening motion of crosshead 35.

The rods 64 bear at their upper end against a blast valveand contact-actuating piston 65 that is integral with the movable blast valve member 36. This piston 65 is of an annular form and surrounds the cylinder 52 with a sliding fit. A suitable O-ring seal 63 is preferably provided to prevent pressurized air from leaking past the piston 65 along the outer surface of cylinder 52. The movable blast valve member 36 is of a cylindrical form and closely surrounds the upper end wall 54, which has a circular outer periphery slidably fitting within the cylindrical blast valve member 36. The outer periphery of the movable blast valve member 65 is slidably mounted within a cylindrical portion 67 of the stationary casting 38 that cooperates with a suitable piston ring on piston 65 to prevent pressurized air from leaking along this outer periphery into the space It)? beneath the piston 65.

The movable blast valve member 36 can be driven in a downward opening direction by supplying pressurized air to an actuating chamber 66 located immediately above the blast valveand contact-actuating piston 65. In this connection, the upper end wall 54 of cylinder 52 extends radially outward past the outer periphery of the cylinder 52 and defines an upper wall for this actuating chamber 66. An inlet passage 69 communicates with this actuating chamber 66. When high pressure air is permitted to flow through this inlet passage 69, as will soon be described, it will flow into the actuating chamber 66 and build up a pressure that acts on the upper surface 65a of the blast valveand contact-actuating piston '65 to drive the piston 65 in a downward blast-valve-opening direction. This upper surface 65a of the piston 65 is referred to hereinafter as the blast valve-opening surface.

This downward movement of the blast valve-and contact-actuating piston 65 withdraws the upper sealing surface 36a of the movable blast valve member 36 from its seat, thereby producing the previously-described blast of gas along the paths 40 of FIG. 1. FIG. 4 illustrates the blast valve member 36 in its fully open position with the high pressure air streaming past its upper surface. Downward movement of the blast valve-and contact-actuating piston 65 into its position of FIG. 4 is also transmitted through the rods 64 and the crosshead 30 to the movable contacts 24. This causes these contacts to open and draw a pair of arcs adjacent the nozzles 38. These arcs are extinguished after a short period by the gas blast through the nozzles.

Pilot valve and its operation For controlling the flow of high pressure air into the blast valve actuating chamber 66 so as to control movement of the blast valve member 36, a normally-closed pilot valve 70 comprising a movable pilot valve member 71 is provided. Referring to FIG. 3, there is a flow passage 72 located centrally of the end wall 54 and a connecting passage 73 that connects the central passage 72 with inlet passage 69. When the movable pilot valve member '71 is in its uppermost position of FIG. 3, an annular sealing surface thereon abuts against a suitable seat on the end wall 54 and thus prevents high pressure air from entering the passages 72, 73 and 69. But when the movable pilot valve member 71 is driven in a downward opening direction into its position of FIG. 4, high pressure air is permitted to flow past thte pilot valve via passages 56, 57, 72, 73, 69 into the blast-valve actuating chamber 66, thus driving the blast valve-and contact-actuating piston 65 in a downward direction to effect the above-described opening of the blast valve member 36 and the movable contacts 24.

Poitassisting in opening the pilot valve member 71 and for holding the pilot valve member 71 in its open position for the desired period, the pilot valve member 71 is provided with a booster piston 75. This booster piston 75 is secured to the upper end of an upwardlyextending extension of pilot valve member 71. The booster piston 75 is slidably mounted within a booster cylinder 76, and a compression spring 77 is located between the booster piston 75 and the end wall 54 to exert an upward biasing force on the movable pilot valve member 71 that normally holds the movable pilot valve member in its closed position of FIG. 3. An actuating chamber 78 for the booster piston 75 is located between the upper surface 79 of the booster piston and the upper end wall of the booster cylinder 76.

The actuating chamber 78 for the booster piston is normally vented to atmosphere through a passage 80 that extends through the extension of the movable pilot valve member 71 into the central flow passage 72. The central flow passage 72 is, in turn, normally vented to atmosphere through a passage 82 and a slot 84 formed in the inner cylindrical surface of blast valve member 36 and aligned with passage 82 when the blast valve is closed. When the movable pilot valve member 71 is moved in a downward direction out of its normally-closed position of FIG. 3, an enlarged portion 85 of its extension covers the entry port 86 to the passage 82, thereby blocking communication between passages 72 and 82, thus sealing the central flow passage 72 from atmosphere. Thus, when the movable pilot valve member 71 is moved in a downward opening direction, the central flow passage 72 is no longer vented to atmosphere and high pressure air flows into the central passage 72 and through the passage 80 into the actuating chamber 78 for the booster piston. This results in a rapid pressure buildup above the booster piston 75 that provides a supplemental opening force for driving the booster piston 75 and the movable pilot valve member 71 downwardly toward their fully-open position of FIG. 4. As will be explained in greater detail hereinafter, this rapidly-developed supplemental force helps to render contact-opening times substantially independent of minor variations in the instant at which the pilot valve member starts its opening movement.

Reset of the movable pilot valve member 71 to its closed position of FIG. 3 is accomplished at a subsequent point by supplying high pressure air to the space 87 beneath the booster piston 75. For supplying this high pressure air for resetting purposes, a pilot valve reset passage 90 is provided leading into the reset space 87. This pilot valve reset passage 90 has an inlet that is located in vertical alignment with the passage 73, but no effective communication normally is present between passages 73 and 90. However, when the movable blast valve member 36 moves into its fully-open position of FIG. 4, an interlock slot 92 formed in its inner surface establishes effec tive communication between passages 73 and 90. This permits high pressure air to flow through passages 73 and 90 via interlock slot 92 and into the reset space 87, thereby building up a pressure in the reset space 87. This pressure acts in an upward direction on the lower surface 75b of booster piston 75. (Note that lower surface 75b includes upper and lower area portions as designated in FIG. 3.) Since force on the lower surface 75b of the booster piston 75 acts in a direction to close the pilot valve 71, then surface 75b will be referred to hereinafter as the pilot valve-closing surface. Since piston 75 has a substantially larger lower surface 7512 than upper surface 79, there is a net force on the piston 75 acting in a direction to return the movable pilot valve member 71 from its position of FIG. 4 to its normallyclosed position of FIG. 3. The compression spring 77 also helps to provide force for this resetting operation. The space immediately surrounding the cup-shaped booster piston 75 is vented to atmosphere through a passage 93 to prevent air from leaking between opposite sides of the booster piston along the outer surface of the piston.

Pneumatic coupling for pilot valve control 'The other piston 102, which will be referred to as the control piston, is connected to an operating rod 104 which extends through an opening in the lower wall 53 of the cylinder 52 and then, as shown in FIG. 1, through a sealed opening in the wall of tank 10 and then through the interior of the insulating support column 12. Suitable operating means, shown in FIGS. 5 and 6, is provided at the lower end of the rod 104 for operating the rod 104 in a downward direction. As will soon appear more clearly, downward movement of the rod produces opening of the circuit breaker, and upward movement of the rod from its open position produces closing of the circuit breaker. The rod 104 preferably passes through the lower end wall 53 of cylinder 52 via a central bore 107 in the dashpot piston rod 61.

When the circuit breaker is in its closed position of FIG. 3, high pressure air is present adjacent both the upper and lower surfaces of both of the two pistons and 102. This follows from the fact that high pressure feed line 56 communicates via ports 57 and 58 with the interior of cylinder 52.

When the operating rod 104 is driven downwardly to pull the piston 102 in a downward direction, the volume between the two pistons quickly increases, producing a sudden drop in pressure in this volume. This drop in pressure permits the high pressure air immediately above piston 100 to develop a large downward force that drives the pilot piston 100 downwardly in follow-up relationship to the lower piston 102. This downward motion of pilot piston 100 opens the pilot valve and thus begins movement of the blast valve member 36 and the contacts 24 toward their respective open positions, as described hereinabove.

The upper piStOn 100 continues moving in pneumatically coupled follow-up relationship to the lower piston 102 until the lower piston crosses the port 58. When this occurs, high pressure air flows through the port 58 into the space 105 between the two pistons, equalizing the pressure on opposite sides of the upper piston 100 to, in effect, break the pneumatic coupling between the two pistons 100 and 102.

But despite this uncoupling of the two pistons 100 and 102, the upper piston does not immediately return to its normal position of FIG. 3. This is the case because the booster chamber 78 has then filled with high pressure air acting in a downward direction on the booster piston 75 and the movable pilot valve member 71. The downward force exerted by this high pressure air holds the pilot valve member 71 in its fully open position until the movable blast valve member as has reached substantially its fully open position.

Closing of the pilot valve near the end 0] a circuit breaker opening operation When the movable blast valve member 36 does reach substantially its fully open position of FIG. 4, its interlock slot 92 establishes communication between passages 73 and 90, as previously described. High pressure air then flows through '73 and 00 via slot 92 and soon builds up a high pressure in the pilot valve reset space 87. The rate at which this pressure buildup occurs is controlled by a manually-adjustable throttle valve 100 located in the passage 90. When the pressure in the pilot valve reset chamber 87 has built up to a predetermined level, a sufficient upward force is exerted on the booster piston 75 to return the movable pilot valve member 71 to its normally-closed position of FIG. 3.

Closing of the blast valve in response to pilot valve closing The movable blast valve member 36 remains in its fully-open position of FIG. 4 until the movable pilot valve member 71 has returned to substantially its normally-closed position of FIG. 3. The force for blast valveclosing is developed in a blast-valve closing chamber 109 at the lower side of the blast-valve piston 65. This cham ber 109 is normally vented to atmosphere. But when the pilot valve member 71 returns to its closed position while the blast valve member 36 is in its fully-open position of FIG. 4, chamber 109 is no longer vented to atmosphere and a pressure-equalizing passageway is present connecting blast-valve actuating chamber 66 and the blast-valve closing chamber 169 at the lower side of the blast valve piston 65. This pressure-equalizing passageway is constituted by passages 69, 73, 72, 86, 82 and 110 and is open when the movable pilot valve member 71, 85 uncovered port 86 near the end of its abovedescribed closing motion. Passage 116 normally vents the blast valve closing space 109 to atmosphere through passages 82 and 84, as seen in FIG. 3. But when the blast valve member 36 is in its fully open position, passage 82 is shut oflf from atmosphere by reason of slot 84 in the movable blast valve member moving out of alignment therewith. When high pressure air flows from the blastvalve actuating chamber 66 to the closing chamber 189 at the lower side of the blast valve piston 65 through the above-described equalizing passage, the pressures on opposite sides of the blast valve piston 65 equalize. It will be apparent from FIGS. 3 and 4 that the blast valve piston has a larger area exposed to pressure in chamber 109 than to pressure in chamber 66. Accordingly, there is then a net force acting in an upward direction on the blast valve piston 65, and this force acts to return the movable blast valve member 36 to its closed position.

The above-described interlocking relationship between the operation of the pilot valve member 71 and the blast valve member 36 is described an greater detail and is claimed in our application S.N. 421,777, filed Dec. 29, 1964, and assigned to the assignee of the present invention.

In order to prevent any substantial build-up of pressure in the blast valve closing chamber 169 while the pilot valve member 71 is in its open position, a vent passage in the form of an external groove 115 is provided in the movable pilot valve member 71. This vent passage 115 vents the passages 110 and 82 to atmosphere through a vent 116 in the end cap 54 aligned with the vent passage 115 while the movable pilot valve member 71 is in its open position of FIG. 4. This venting means 115, 116 insures that any leakage of high pressure air into blast valve closing chamber 189 (when the blast valve is open and vent 84 in the blast valve member 36 is therefore unavailable) will not build up a significant pressure in chamber 109. Preventing such pressure buildup assures that closing of the movable blast valve member 36 will not be initiated until the pilot valve member 71 has returned to nearly its fully closed position of FIG. 3.

The rate at which pressure is built up in blast valve closing space 109 can be controlled by a needle valve 120 that can be adjusted to control the rate of flow through the pressure equalizing passage 69, 73, 72, 86, 82, 110.

When the blast valve member 36 is in its closed position, illustrated in FIG. 3, it has a' larger area exposed to pressure acting in a closing direction than in an opening direction, and this results in a force normally holding the blast valve member 36 closed. To assure that the blast valve member 36 remains closed even through there might be a large drop in tank pressure, a plurality of light compression springs 119, shown in FIG. 2, are provided in the chamber 109 beneath the blast valve piston. These springs 119 act in an upward direction against the blast valve piston 65 to resist downward opening movement of the blast valve member 36.

When the movable blast valve member 36 closes, as hereinabove described, in response to prior pilot valve closing, all the chambers upstream from the sealing surface of the pilot valve member 71 are vented to atmosphere. The manner in which such venting takes place can best be seen in FIG. 3, where both the pilot valve member 71 and blast member 36 are shown in their respective closed positions. Referring to FIG. 3, it will be apparent that the blast valve closing chamber 109 is vented to atmosphere through passages 110, 82, and 84; whereas the blast valve actuating chamber 66 is vented-to atmosphere through passages 69, 73, 72, 82 and 84. The booster piston actuating chamber 78 is vented to atmosphere through passages 86, 82 and 84. The pilot valve reset chamber 87 is vented through small bleed passages 123 and 124 communicating with passage and then through passages 82 and 84. Venting of these chambers at this time serves the desirable function of assuring that on a subsequent operation, pressures will be built up in these chambers from the same reference level, i.e. atmospheric pressure. This helps to assure that the blast valve-opening and contact-opening times will not vary appreciably from one opening operation to the next. Also venting the blast valve closing chamber 109 assures that there will be no pressure in this chamber acting downwardly on the ends of rods 64 to interfere with a subsequent circuit breakerclosing operation, when the rods 64 more upwardly through chamber 109, as will soon be described.

The passages 123 and 124 leading into pilot valve reset chamber 87 function as a portion of a pneumatic lock for folding the pilot valve closed during the period between return of the pilot valve to its closed position and return of the blast valve member 36 to its closed position. More specifically, these passages 123, 124 assure that the pilot valve will not be opened unintentionally by any pressure differential developing on opposite sides of the booster piston 75 while the blast valve member 36is open and booster chamber 78 is therefore unvented. In this regard, these passages 123, 124 maintain communication between chamberas 78 and 87 on opposite sides of the booster piston 75 while the pilot valve is in closed position. Thus, any high pressure present in booster piston actuating chamber 78 will also be present in the reset chamber 87, and there will be a net force on booster piston 75 acting in a pilot valve-closing direction to hold the pilot valve closed in view of the relatively large cosing area 75b as compared to opening area 79.

On an opening operation, the high pressure air that flows through passage 80 will fiow almost entirely into the booster piston actuating chamber 78, with little entering the reset chamber 87 through passages 123, 124. This is the case because passage 123 is a small bleed passage and, due to its small size, does not permit much high pressure to flow into chamber 87 during the brief period before the passage 123 is covered by an enlarged portion 126 on movable pilot valve member 71. Near the end of a pilot valve-opening stroke, this enlarged portion 126 acts as a dash-pot piston in a cylinder 127. Air displaced from cylinder 127 by piston 126 is forced through passage 124 which becomes progressively more restricted as the pilot valve member 71 reaches the end of its opening stroke.

Holding the contacts and the control piston in open position After the crosshead 30 has been driven downwardly by the blast valve-and contact-actuating piston 65 to open the contacts 24, as described hereinabove, the crosshead 30 is latched in its open position by a mechanical latch 13%) shown in FIG. 5. This latch 13th holds the crosshead 30 and the interconnected contact 24 in their open positions of FIGS. 4 and 6 despite the above-described return of the blast valve member 36 to its closed position. In this connection, a suitable roller 132 carried by the crosshead 30 normally holds the latch 132' in its released position shown in FIG. 5, where the circuit breaker is depicted closed. When the circuit breaker is operated toward open position and the roller 132 moves downwardly past the lower end of latch 131), a reset spring 134 drives the latch clockwise about its stationary pivot 135 against a stop 136. The latch is then in its latching postion of FIGS. 4 and 6, where it can prevent upward movement of the crosshead 30 through interference with roller 132, thus holding the contacts open. 7 v

The control piston 162 that was moved downwardly to initiate pilot valve opening is similarly held in its loWermost position of FIG. 6 by a latch schematically depicted at 140. A closure-initiating spring 142 acts on operating rod 104 to bias the piston 102 upwardly toward its initial position of FIG. 5, but the latch 140 retains the piston 102 in its lowermost position so long as it is desired to hold the circuit breaker open.

The latch 140 acts on a force-transmitting linkage 170 which is coupled to the rod 104. This force-transmitting linkage 170 comprises a plurality of cranks 172, 173, and 174, which are respectively pivotally mounted on stationary pivats 172a, 173a and 174a. interconnecting the cranks 172 and 173 is a link 1'75 pivotally connected at its opposite ends to the two cranks. Interconnecting the cranks 174 and 173 is a link 176 pivotally connected at its opposite ends to these two cranks. The crank 174 carries a latching roller 177 which the latch 140 cooperates with to hold the linkage in its position of FIG. 6.

Closing operation of the Circuit breaker Closing of the circuit breaker is initiated by suitably tripping the latch 140 of FIG. 6. This is done with a solenoid 144 that, upon energization, drives its armature upwardly to engage the latch 140 and pivot it counterclockwise about its stationary pivot 146 against the bias of a latch-reset spring 145. This removes the restraining eifect of the latch 140 from the latching roller 17?, permitting the closurednitiating spring 142 near the top of rod 104 to drive the control piston 102 and operating rod 104 upwardly. Upward movement of the operating rod 104 moves the linkage 1'70 into its unlatched position of FIG. 5.

The above-described upward movement of the operating rod 104 is used for releasing the contact-restraining latch 130 after a predetermined amount of such upward movement of the operating rod 104. Release of the contact-restraining latch 130 is ettected by means of a latchreleasing linkage 180 that is coupled between the operating rod 104 and the contact-restraining latch 130. This latch-releasing linkage 180 comprises an input arm 181 that is pivotally mounted on a stationary pivot 182 and an output arm 183 that is pivotally mounted on a stationary pivot 104. These arms 181 and 183 are interconnected by a link 185 that is pivotally connected at its opposite ends to the respective arms. The input arm 181 has a pivotal connection 186 at its outer end with the operating rod 104. The output arm 103 carries a roller 107 that is adapted to engage the contact-restraining latch 130. When the operating rod 104 moves upwardly, it acts through parts 181 and 185 to pivot arm 103 clockwise about its pivot 184, causing roller 187 to engage the latch 130 and pivot it in a counterclockwise releasing direction. After a predetermined upward movement of operating rod 104, the latch 1350 is released.

Release of the latch 130 allows the high pressure air acting on the crosshead 30 to drive the crosshead upwardly, thereby pivoting the movable contact 24 of FIG. 4 in a counterclockwise direction about stationary pivot 26 to effect circuit breaker closing. There is an upwardlyacting pneumatic bias on the crosshead 30 because the rods 64 extended into the vented chamber 109 and therefore had no high pressure air acting downwardly on them. There is thus a larger area of the crosshead structure 30, 64 exposed to pressure acting in an upward closing direction than to pressure acting in a downward direction.

The contact-closing speed is controlled by piston 150 attached to the crosshead 30. This piston 150 is slidably mounted in a stationary cylinder 152 having a large opening 154 therein. Initial closing motion takes place at high speed since the air in cylinder 152 ahead of the upwardly moving piston 150 can be freely expelled through opening 154. But when the upwardly moving piston 150 passes the opening 154, the air ahead of it is forced through a restricted passage 156 at a controlled rate, thus providing a dashpot action that smoothly terminates upward closing movement of the piston 150 and the connected contacts.

10 To prevent a retarding low pressure from being developed above piston during downward opening movement, a passage 157 containing a check valve 158 is provided in the piston to allow air to flow upwardly into the space above the piston should a reduced pressure be developed in this space.

To prevent a retarding low pressure from being developed behind the opening dashpot piston 60 during closing, a passageway is provided leading from the high pressure tank into the cylinder space behind the piston 60. A check valve 162 in this passage 160 allows air to flow upwardly therethorugh into the space behind the piston 60 as it moves upwardly. This check valve prevents air from flowing through passage 160 during an opening operation.

When the control piston 102 moves upwardly during the abovedescribed closing action, the high pressure air in cylinder 52 ahead of the piston 102 is expelled first primarily through the port 58 and then through the check valves 148, 149 in the pistons 100 and 102, respectively. At the end of the upward stroke there is high pressure air on both sides of each of the two pistons 100 and 102. Although one check valve has been shown in each piston 100, 102, we preferably use several in each piston to permit a freer flow of air from the space between the pistons during closing. The position of the parts at the end of the closing operation is depicted in FIG. 3.

It will be apparent that when the control piston 102 moves upwardly and returns to its position of FIG. 3, it is once again pneumatically coupled to the pilot piston 100. Accordingly, when a subsequent opening operation, the control piston 102 is moved downwardly, the pilot piston 100 will move behind it in coupled follow-up relationship.

T he motor for controlling opening of the pilot valve For eflecting the above-described downward movement of control piston 102 in order to initiate a circuit breaker opening operation, a fluid motor 190 is provided at the end of force-transmitting linkage 170. This fluid motor 190 comprises a reciprocable piston 191 that is slidably mounted in a stationary cylinder 192. When pressurized air is supplied to the cylinder space beneath piston 191, piston 191 moves rapidly upward, pivoting the crank 174 clockwise about its stationary pivot 174a and thereby rapidly pulling the operating rod 104 downwardly by force transmitted through the linkage 170. This downward movement of operating rod 104 causes the pilot valve 70 to open, thereby initiating a circuit breaker-opening operation, as described hereinabove.

When the piston 191 reaches the top of its upward pilot valve-opening stroke, as shown in FIG. 6, the pressurized fluid beneath it is vented to a low pressure region, and the piston 191 quickly returns to its lowermost position of FIG. 5 in response to such venting. A suitable reset spring 193 is provided to facilitate this resetting operation. The flow of pressurized fluid into and out of the cylinder spaced beneath piston 191 is controlled by suitable threeway valve 195 that in its normal position vents the cylinder space to a low pressure region. When the valve 195 is opened, as by energizing its solenoid operator 1%, the valve establishes communication between a high pressure source and the cylinder space and also isolates the cylinder space from the low pressure region. At the end of the upward opening stroke of piston 191, valve 195 is returned (by conventional means, not shown) to its normal position to vent the cylinder space and permit resetting of piston 191.

It should be apparent that the fluid motor 190 needs to develop only a relatively low force in order to initiate an opening operation. This is the case because this fluid motor does not directly actuate the blast valve member 36 or the contacts 24 but merely operates the small pilot valve 70. This pilot valve, in turn, initiates operation of the relatively massive blast valve and contacts by controlling the flow of pressurized fluid into the actuating chamber 66 above the blast valve-actuating piston 65.

Rapid build-up of force for opening circuit breaker When a circuit breaker opening operation is to be initiated, the pressure in blast valve-actuating chamber 66 can be built up very quickly because there is only a very small volume upstream from the pilot valve 70 that needs to be filled with pressurized fluid in order to develop a pressure build-up in the actuating chamber 66. In this respect, the actuating chamber 66 itself is quite small, and the passageways '72, '73 and 69 between the pilot valve 70 and the actuating chamber 66 are quite short, as will be apparent from FIG. 3. Hence a very rapid pressure build-up in chamber 66 is possible when the pilot valve 70 is opened. An important factor in keeping the passages 72, 73, 69 short so as to permit a high rate of pressure build-up is that the pilot valve 70 is located immediately adjacent the actuating chamber 66 and in a generally central position with respect to the actuating chamber 66.

It will be apparent that locating the pilot valve '70 generally centrally of the actuating chamber 66 also contributes to the compactness of the operating mechanism since no space outside the piston 65 is required for the pilot valve. Locating the pneumatic coupling 100, 132 in a cylinder space surrounded by annular actuating piston 65 also contributes to the compactness of the operating mechanism by obviating the need for external space to contain such coupling.

Rapid response to a closing signal It will be noted that the above-described closing of the contacts was initated and controlled without requiring any simultaneous venting of a pressurized space ahead of the contact controlling mechanism. In certain prior mechanisms of this general type, it has been the practice to use pressurized fluid in the blast valve closing space, such as 109, to hold the contacts open. When it was decided to close the contacts, this space was vented to atmosphere. When this venting reduced the pressure to a predetermined level, closing was initiated and the closing speed was thereafter controlled by the rate of venting.

In certain circuit breaker applications, it is disadvantageous to rely upon such venting because it tends to be a rather slow operation that unduly delays initiation of contact closing motion and unduly retards the closing motion once initiated. Also, closing characteristics tend to vary rather widely with variations in the initial fluid pressure holding the contacts open. This lack of precision in initiating and controlling the closing operation can be a serious disadvantage in those circuit breaker applications where it is desired to close the contact at a precise instant after the occurrence of some predetermined event, such as the insertion of a voltage-controlling resistor in the power circuit.

In the circuit breaker of the present invention, closing motion of the contacts is initiated by releasing the latch 130. There is no appreciable opposition from pressurized fluid in the blast valve-closing chamber 1% at the time of such latch-release inasmuch as this chamber 109 had previously been vented to atmosphere at the time the blast valve member 36 closed, as described hereinabove. Hence, unlike in prior mechanisms, there is no delay in the initiation of closing motion while such space is be ing vented to develop a force for closing. In our mechanism, closing force is available even before latch release inasmuch as there is a net force acting in a closing direction on the contacts as soon as this space 189 is vented, and such venting occurs long before release of the latch 13%. This closing force which is available at the time of latch-release can drive the contacts in a closing direction with no appreciable delay, and the speed of closing can be more precisely controlled since it does not depend upon the previously-used venting. Still further, using a fluid pressure-derived force for closing the contacts has certain advantages over using'a spring-derived force in that there is no force gradient to diminish the available force as the contacts near their closed position. Thus, a

high closing force is available at the end of a closing operation to overcome the opposition of any magnetic forces that are developed at this point by high currents flowing through the contacts when they reestablish the power circuit at the end of a closing stroke.

Insensitivity of opening time to initial spacing between pilot and control pistons It should be noted that the blast valve-opening times and the contact-opening times are substantially independent of small variations in the length of the gap initially present between the pistons and N2 when a circuit breaker-opening operation is begun. One factor responsible for this substantial insensitivity to gap length is that high pressure builds up so quickly above the booster piston 75 once the pilot valve member 71 starts moving toward open position that the pilot piston 100 is immedi ately driven into engagement with the adjacent downwardly-moving control piston 102. Thereafter, the opening speed of the pilot piston 100 is the same as the opening speed of the control piston 102. If a longer initial gap was present between the pistons 100 and 102, motion of the pilot piston would be initiated at a slightly later instant relative to the instant at which motion of control piston 102 had been initiated, but this late start would be compensated for by the higher initial speed at which the booster piston '75 would drive the pilot piston 100 when there was more space between pistons tilt) and 102. After a very short period, the pilot piston 160 would have reached the same point in its opening travel as it would have reached had it started its opening travel slightly earlier. A slightly earlier start at a lower speed would not appreciably increase the time for pressure to build up to an effective level in blast valve actuating chamber 66 because when the pilot valve is just beginning to open, very little air can flow past it, particularly if the opening speed is relatively low. Thus, pressure builds up to an effective level in the actuating chamber 66 in about the same time irrespective of minor variations in the length of the gap between pistons 1% and 102. Accordingly, if for any reason there should be minor variations in the initial position of the control piston 102, these variations will not appreciably affect the circuit breaker opening times. a

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and We therefore intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. In a gas blast circuit breaker comprising a contact movable from a closed position to an open position to develop an arc and a blast valve member movable from a closed position to an open position to create an arcextinguishing blast,

(a) a tank adapted to contain a supply of high pressure gas in which said contact is located,

(b) a blast valve-actuating piston coupled to said movable blast valve member,

(c) said piston having an opening surface on which pressurized fluid is adapted to act in a blast valveopening direction and a closing surface on which pressurized fluid is adapted to act in a blast valveclosing direction,

(d) means for supplying high pressure fluid to the opening surface of said piston to drive said piston through an opening stroke that opens said blast valve member,

(e) actuating means coupled to said contact for transmitting contact-opening motion from said blast valveactuating piston to said contact when said blast valve-actuating piston moves through said opening stroke,

(f) means for supplying high pressure fluid to the closing surface of said piston after said opening stroke to cause closing of said blast valve member,

(g) means for venting the closing surface of said piston to a low pressure region when said blast valve member is closed, thereby removing from said closing surface high pressure fluid that previously acted on said contact in an opening direction,

(h) closing means for causing the high pressure gas in said tank, when the closing surface of the blast valve piston is vented to a low pressure region, to exert a net force on said contact acting in a direction to drive said contact toward closed position,

(i) latching means for holding said Contact in an open position against said closing means when said closing surface of said piston is vented to said low pressure region,

(j) and closing control means for releasing said latching means to permit said closing means to drive said contact into closed position.

2. An electric circuit breaker of the gas-blast type comprising:

(a) a tank adapted to contain a supply of high pressure (b) a first contact within said tank,

. (c) a second contact Within said tank movable relative to said first contact between a closed position and a fully-open position,

(d) opening means for moving said second contact from said closed to said fully open position,

(e) means for rendering said opening means ineffective to exert continued opening force on said second contact when said second contact has reached said fully open position,

(f) closing means for causing the high pressure gas in said tank, when said opening means is rendered ineffective, to exert a net force on said second contact acting in a direction to drive said second contact toward closed position,

(g) releasable latching means for holding said second contact in said fully open position when said open- I ing means is rendered ineffective,

(h) and closing control means for releasing said latching means to permit said closing means to drive said second contact into closed position.

3. The circuit breaker of claim 2 in combination with:

(a) a pilot valve having a normal condition from which it is operable to produce operation of said opening means,

(b) pilot valve operating means releasably coupled to said pilot valve for causing said pilot valve to operate and produce operation of said opening means,

(c) means for releasing said pilot valve operating means from coupled relation with said pilot valve to permit return of said pilot valve to its normal condition;

(d) means for returning said pilot valve operating means to coupled relationship with said pilot valve,

(e) said closing control means being responsive to said return of the pilot valve operating means for effecting release of said latching means.

4. An electric circuit breaker of the gas blast type comprising:

(a) a tank adapted to contain a supply of high pressure gas,

(b) a movable blast valve member movable from a normally-closed position to an open position to create an arc-extinguishing blast of gas from said tank,

(c) mounting structure located within said tank and having a passageway therein communicating with the high pressure air in said tank,

((1) a generally annular blast valve-controlling piston surrounding said mounting structure and slidably mounted thereon,

(e) means coupling said annular piston to said movable blast valve member,

(f) means defining a blast valve-opening chamber at one side of said annular piston where pressurized fluid is adapted to exert a force for driving said piston in a blast valve-opening direction,

(g) means defining a blast valve-closing chamber at the other side of said annular piston where pressurized fluid is adapted to exert a force for driving said piston in a blast valve-closing direction,

(h) means including a normally-closed pilot valve located in said mounting structure and openable to permit high pressure fluid to flow from said passageway in said mounting structure into said blast valveopening chamber to drive said piston through a blast valve-opening stroke,

(i) and means controlled by said pilot valve for supplying high pressure air to said closing chamber to effect closing of said blast valve member after opening thereof.

5. The electric circuit breaker of claim 4 in combination with:

(a) a circuit-controlling contact movable between a closed position and an open position,

(b) contact-actuating means driven by said blast valve controlling piston for imparting opening motion to said contact during a blast valve-opening stroke,

(c) and means for holding said contact in open position when said blast valve member closes.

6. The electric circuit breaker of claim 4 in combination with:

(c) said contact actuating means comprising a forcetransmitting member coupled to said contact and slidably mounted on said mounting structure and a plurality of rods coupled to said force-tranmitting member and projecting therefrom through said blast valve closing chamber into engagement with said blast valve-controlling piston,

(d) and means for holding said contact in open position when said blast valve member closes.

7. The circuit breaker of claim 4 in which said mounting structure has a cylinder space therein and said pilot valve comprises a movable flow-controlling pilot valve member, the circuit breaker further comprising:

(a) a pilot piston slidably mounted in said cylinder space and coupled to said movable pilot valve member,

(b) and means for controlling movement of said pilot piston comprising a control piston slidably mounted in said cylinder space adjacent said pilot piston and pneumatically coupled to said pilot piston during predetermined movement of said control piston.

8. In a gas blast circuit breaker comprising a contact movable from a closed position to an open position to develop an arc and a blast valve member movable from a closed position to an open position to create an arcextinguishing blast,

(a) a blast valve actuating piston coupled to said movable blast valve member,

(b) said actuating piston having an opening surface on which pressurized fluid acts in a blast valveopening direction,

(c) a normally-closed pilot valve comprising a movable pilot valve member having a normally-closed position for closing said pilot valve and an open position for opening said pilot valve,

(d) means including said normally-closed pilot valve for supplying high pressure fluid to said opening surface when said pilot valve is opened, thereby driving said actuating piston through a blast valve-opening stroke,

(e) a pilot piston coupled to said movable pilot valve member,

(f) a cylinder in which said pilot piston is slidably mounted,

(g) a control piston slidably mounted in said cylinder adjacent said pilot piston,

(h) means for moving said control piston in a direction away from said pilot piston,

(i) means for pneumatically coupling said pilot piston to said control piston so that said pilot piston moves in follow-up relation to said control piston and imparts opening movement to said movable pilot valve member,

(j) means for rendering said pneumatic coupling inetfective after a predetermined movement of said control piston so that said movable pilot valve member can return to its normally-closed position free of said control piston,

(k) means responsive to return of said pilot Valve member to its closed position to effect closing of said blast valve member,

(l) actuating means coupled to said contact and driven by said blast valve-actuating piston for imparting contact-opening movement to said contact in response to blast valve-opening movement of said blast valveactuating piston,

(m) and latching means for holding said contact in an open position following closing of said blast valve member by its actuating piston.

9. The circuit breaker of claim 8 in which said blast valve-actuating piston has a closing surface on which pressurized fluid is adapted to act in a blast valve-closing direction and in which said means for effecting closing of said blast valve member comprises means for supplying high pressure fluid to said blast valve-closing surface when said movable pilot valve member returns to its closed position.

10. The circuit breaker of claim 8 in combination with:

(a) releasable restraining means for holding said con trol piston in a position that it enters after causing .pilot valve-opening movement of said pilot piston,

(b) closure-initiating means for returning said control piston to its normally-closed position adjacent said pilot piston in response to release of said restraining means, i

(c) means responsive to passage of said control piston through an intermediate point in its return stroke for releasing said latching means to permit said contact to close,

(d) and means responsive to release of said latching means to drive said contact into closed position.

11. In a gas blast circuit breaker comprising a contact movable from a closed position to an open position to develop an arc and a blast valve member movable from a closed position to an open position to create an arcextinguishing blast,

(a) a blast valve-actuating piston coupled to said movable blast valve member,

(b) said actuating piston having an opening surface on which pressurized fluid acts in a blast valve-opening direction,

(c) a normally-closed pilot valve comprising a movable pilot valve member having a normally closed position for closing said pilot valve and an open position for opening said pilot valve,

(d) means including said normally-closed pilot valve for supplying high pressure gas to said opening surface when said pilot valve is opened, thereby driving said actuating piston through a blast valve-opening stroke,

(e) means for moving said movable pilot valve member into an open position and for thereafter returning 16 said pilot valve member to its normally-closed position while said blast valve member is still open,

(f) means responsive to return of said pilot valve member to its closed position to effect closing of said blast valve member,

(g) actuating means coupled to said contact and driven by said blast valve-actuating piston for imparting contact-opening movement to said contact in response to blast valve-opening movement of said blast valveactuating piston,

(h) and latching means for holding said contact in an open position following closing of said blast valve member by its actuating piston.

12. The circuit breaker of claim 11 in which said blast valve-actuating piston has a closing surface on which pressurized fluid is adapted to act in a blast valve-closing direction and in which said means for effecting closing of said blast valve member comprises means for supplying high pressure fluid to said blast valve-closing surface when said movable pilot valve member returns to its closed position.

13. The circuit breaker of claim 11 in which said means for moving said pilot valve member into an open position comprises a driving member releasably coupled to said pilot valve member, and in which means is provided for releasing the coupling between said driving member and said pilot valve member after a predetermined movement of said driving member to then permit closing movement of said pilot valve member.

14. The circuit breaker of claim 11 in which said means for moving said pilot valve member into an open position comprises a driving member releasably coupled to said pilot valve member, and in which means is provided for releasing the coupling between said driving member and said pilot valve member after a predetermined movement of said driving member to then permit closing movement of said pilot valve member, said circuit breaker further comprising:

(a) releasable restraining means for holding said driving member in a position that it enters after causing opening movement of said pilot valve member,

(b) closure-initiating means for returning said driving member to a position where it is coupled to said pilot valve member in response to release of said restraining means,

(c) means responsive to passage of said driving member through an intermediate point in its return stroke for releasing said latching means to permit said contact to close,

((1) and means responsive to release of said latching means to drive said contact into closed position.

15. In an electric circuit breaker comprising a contact movable from a closed position to an open position to 7 effect circuit-interruption,

(a) a contact-actuating piston having an opening surface on which pressurized fluid is adapted to act in a contact-opening direction,

(b) means for transmitting contact-opening motion from said piston to said contact when said piston moves in a contact-opening direction,

(c) means comprising a pilot valve for controlling the motion of said contact-actuating piston,

(d) said pilot valve comprising a movable pilot valve member having a normally-closed position for blocking pressurized fluid from reaching said opening surface and an open position for permitting .pressurized fluid to reach said opening surface,

(e) a pilot piston coupled to said movable pilot valve member,

(f) a cylinder in which said pilot piston is slidably mounted,

(g) a'control piston slidably mounted in said cylinder adjacent said pilot piston,

(i) means for pneumatically coupling said pilot piston to said control piston so that said pilot piston moves in follow-up relationship to said control piston and imparts opening movement to said pilot valve member,

(j) booster means effective when operative to apply a supplemental opening force to said pilot valve member to accelerate opening movement of said pilot valve member and to urge said pilot piston toward said control piston,

(k) and means controlled by initial opening movement of said pilot valve member to render said booster means operative upon initial opening movement of said .pilot valve member.

16. The circuit breaker of claim 15 in combination with a normally-closed blast valve member that is openable to produce a fluid blast that facilitates circuit interruption and means responsive to movement of said contact-actuating piston in a contact-opening direction for producing opening of said blast valve member.

18 17. The circuit breaker of claim 15 in combination with a housing at high voltage surrounding said contact, said contact-actuating piston, said pilot valve, said pilot piston, said control piston, and said booster means; insulating means on which said housing is mounted; and means extending from said control piston to a location outside said tank for imparting motion from said outside location to said control piston.

References Cited UNITED STATES PATENTS 2,783,337 2/1957 Beatty et al. 200148 2,783,338 2/1957 Beatty 200-148 3,214,540 10/1965 Schrameck et al. 20 148 ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examin r.

Claims

1. IN A GAS BLAST CIRCUIT BREAKER COMPRISING A CONTACT MOVABLE FROM A CLOSED POSITION TO AN OPEN POSITION TO DEVELOP AN ARC AND A BLAST VALVE MEMBER MOVABLE FROM A CLOSED POSITION TO AN OPEN POSITION TO CREATE AN ARCEXTINGUISHING BLAST, (A) A TANK ADAPTED TO CONTAIN A SUPPLY OF HIGH PRESSURE GAS IN WHICH SAID CONTACT IS LOCATED, (B) A BLAST VALVE-ACTUATING PISTON COUPLED TO SAID MOVABLE BLAST VALVE MEMBER, (C) SAID PISTON HAVING AN OPENING SURFACE ON WHICH PRESSURIZED FLUID IS ADAPTED TO ACT IN A BLAST VALVEOPENING DIRECTION AND A CLOSING SURFACE ON WHICH PRESSURIZED FLUID IS ADAPTED TO ACT IN A BLAST VALVECLOSING DIRECTION, (D) MEANS FOR SUPPLYING HIGH PRESSURE FLUID TO THE OPENING SURFACE OF SAID PISTON TO DRIVE SAID PISTON THROUGH AN OPENING STROKE THAT OPENS BLAST VALVE MEMBER, (E) ACTUATING MEANS COUPLED TO SAID CONTACT FOR TRANSMITTING CONTACT-OPENING MOTION FROM SAID BLAST VALVEACTUATING PISTON TO SAID CONTACT WHEN SAID BLAST VALVE-ACTUATING PISTON MOVES THROUGH SAID OPENING STROKES, (F) MEANS FOR SUPPLYING HIGH PRESSURE FLUID TO THE CLOSING SURFACE OF SAID PISTON AFTER SAID OPENING STROKE TO CAUSE CLOSING OF SAID BLAST VALVE MEMBER, (G) MEANS FOR VENTING THE CLOSING SURFACE OF SAID PISTON TO A LOW PRESSURE REGION WHEN SAID BLAST VALVE MEMBER IS CLOSED, THEREBY REMOVING FROM SAID CLOSING SURFACE HIGH PRESSURE FLUID THAT PREVIOUSLY ACTED ON SAID CONTACT IN AN OPENING DIRECTION, (H) CLOSING MEANS FOR CAUSING THE HIGH PRESSURE GAS IN SAID TANK, WHEN THE CLOSING SURFACE OF THE BLAST VALVE PISTON IS VENTED TO A LOW PRESSURE REGION, TO EXERT A NET FORCE ON SAID CONTACT ACTING IN A DIRECTION TO DRIVE SAID CONTACT TOWARD CLOSED POSITION, (I) LATCHING MEANS FOR HOLDING SAID CONTACT IN AN OPEN POSITION AGAINST SAID CLOSING MEANS WHEN SAID CLOSING SURFACE OF SAID PISTON IS VENTED TO SAID LOW PRESSURE REGION, (J) AND CLOSING CONTROL MEANS FOR RELEASING SAID LATCHING MEANS TO PERMIT SAID CLOSING MEANS TO DRIVE SAID CONTACT INTO CLOSED POSITION.